Validation of 3D Synthesis RPV Neutron Fluence Calculations using VVER-1000 Ex-Vessel Reference Dosimetry Results (Invited Paper)

3D synthesis based on detailed and improved calculations by SN-codes DORT, ANISN and the BUGLE-96 library has been validated using reference activation data from the Balakovo-3 ex-vessel dosimetry benchmark. The 3D spatial neutron source distribution including pin-to-pin power variations and the complex baffle construction were modeled in detail. All particulars of reactor operation such as coolant temperature changes, assembly power asymmetry and fuel burnup influence on space-energy neutron source distributions were taken into account.
The discrepancies found do not exceed 10%. The average relation between calculated and measured valuse is 0,99. The calculated results show a systematic underestimation for 237Np(n,f) ( -6% on the average), 93Nb(n,n') ( -8%) and systematic overestimation for 58Ni(n,p) and 54Fe(n,p) ( +7%). Generally, the agreement between experiment and calculation is even closer as expected from uncertainty considerations.